"People think there needs to be 40 degree days, and 100 kph winds, that's not the case," he said.

"We've got such a dry environment, fuels are available to burn, and we don't need all of those factors to see intense fires, that was proven yesterday in Kilmore, the winds were 30 - 40 kph, but were challenging to control.

"The key message is be aware that in the heat of the day, mid 30 degree temperatures and wind speeds of 30 -40 kph will have intense fires."

He says three fires remain a concern

Commissioner Lapsley says the Kilmore, Morwell and east Gippsland fires are still of concern.

"The open cut mine is still burning, but it has not impacted on the ability to produce power," he said.

"It is causing some level of difficulties to suppress.

"We're looking at an extinguishing strategy on how to stop the fire, that in itself is a problem in a sense that it is putting significant black smoke over Morwell, and is causing concern."

He says the east Gippsland fires have not moved much in the last 24 hours due to the weather conditions, but says the fire is still in deep seated forested areas and significant resources remain there.

Smoke visible across Victoria

The CFA says there has been widespread smoke from the Kilmore fires, which has spread in to central Victoria and the metropolitan area.

The control tower at Melbourne Airport was evacuated briefly when winds blew smoke from the fires south.

However, the tower has been deemed safe and normal operations will resume shortly.

No significant delays are expected.

Police hunt arsonists

The CFA says smoke across the state will be visible for several days.

Police have investigated 16 fires, 9 of which they have confirm were deliberately lit.

Police Commissioner Ken Lay says one investigation has concluded after an 11-year old boy was cautioned and a 9-year old was released due to his age in relation to a fire at Long Gully.

"Arson is complex, we've seen evidence of quite young children lighting fires," he said.

Commissioner Lay says others light fires with clear criminal intent.

He says other people have been "totally reckless" with tools and machinery.